1. Field of the Invention
The present invention relates to a continuous firing furnace and a manufacturing method of a porous ceramic member using the same, porous ceramic member, and ceramic honeycomb filter.
2. Discussion of the Background
There have been proposed various exhaust gas purifying honeycomb filters and catalyst supporting bodies which are used for purifying exhaust gases discharged from internal combustion engines of vehicles, such as a bus, a truck and the like, and construction machines and the like.
With respect to such an exhaust gas purifying honeycomb filter and the like, there has been used a honeycomb structural body made of a non-oxide ceramic porous material such as silicon carbide or the like having superior heat resistance.
Conventionally, upon firing a ceramic member of this type, there has been used a firing furnace the inner atmosphere of which can be set to an inert gas atmosphere or the like.
With respect to the firing furnace of this type, JP-A 1-290562 (1989) has disclosed a method in which firing containers, each housing an object to be fired, are piled up in multiple stages so that the objects are fired in the firing furnace. Herein, with respect to the firing container, a firing container which has a material chamber for housing the object to be fired and a gas discharging chamber is used, and a gas supplied to the firing furnace is introduced into the material chamber and the gas discharging chamber of the firing container, with the pressure of the gas inside the material chamber being maintained higher than the pressure of the gas inside the gas discharging pressure.
Moreover, JP-A 2003-314964 has disclosed an atmospheric firing furnace that comprises a gas exchanging furnace at each of the inlet and the outlet of the firing furnace. This firing furnace has a valve that is used upon opening an air-sealing door placed between the firing furnace main body and a gas exchange chamber so as to set the firing furnace main body and the gas exchange chamber to the same pressure, so that the opening and closing operations of the door are easily carried out.
However, the firing method disclosed in JP-A 1-290562 (1989) mainly describes a method as to how to allow the gas to flow through the inside of the firing container (jig-for-firing), and this method does not describe anything about atmospheric gas flows with respect to the entire firing furnace. Moreover, FIG. 5 of JP-A 1-290562 (1989) shows only gas flow directions in a space (hereinafter, referred to as muffle) in which an object to be fired is directly placed, such as the inside of the muffle or the like, and does not show anything about atmospheric gas flows including portions outside of the muffle.
The contents of Japanese Patent Laid-open Publication No. 1-290562 (1989) and Japanese Patent Laid-open Publication No. 2003-314964 are incorporated herein by reference in their entirety.